1. Field of the Invention
The present invention relates to a fluorescent endoscopic device and a method of creating a fluorescent endoscopic image for diagnosing a normal tissue and a lesion tissue by obtaining a reflection light image and a fluorescent image.
2. Description of the Related Art
Recently, endoscopes have been widely used in the medical field and the industrial field. Particularly, in the medical field, proposals have been made on technologies for obtaining an image in which a normal tissue and a lesion tissue can be easily discriminated in addition to endoscopic devices for obtaining usual images by usual white light.
For example, using a nature that a normal tissue and a lesion tissue emit different fluorescent intensity of auto-fluorescence if excitation light in an excited wavelength region of a biologically-inherent fluorescent substance is irradiated to a living tissue, such a technology is proposed that local existence of a lesion tissue and an infiltrated range are displayed as fluorescent images by irradiating the excitation light in a predetermined wavelength region to the living tissue and by receiving fluorescent light emitted from the biologically-inherent fluorescent substance.
Since the fluorescent intensity from the living tissue is extremely weak, S/N of the measured fluorescent image is extremely low. Therefore, if standardized calculation is carried out using such a fluorescent image, the S/N of a calculated image on the basis of an obtained calculation value also becomes extremely low, and discrimination between a normal tissue and a lesion tissue becomes extremely difficult.
Then, in Japanese Patent Application Laid-Open Publication No. 2001-314366 and the like, for example, with a purpose of improving S/N and contrast when a calculated image is created by carrying out the standardized calculation on the basis of a ratio between two types of fluorescent images, a device for adding an offset value to each image, respectively, before the standardized calculation is disclosed.